A jury in New York found former NRA gun lobby chief Wayne LaPierre liable on Friday for corruptly mismanaging the organisation.

Lapierre and a senior executive of the National Rifle Association must pay a penalty of US$6.35 million "for years of corruption and greed," said state attorney general Letitia James.

LaPierre, facing a civil trial where he was accused of using the National Rifle Association as a personal piggy bank, was found by the jury to have cost the organisation US$5.4 million because of his misconduct -- although he has since repaid US$1 million of that.

LaPierre said in January he would step down as president of the NRA, citing unspecified health reasons.

James brought a lawsuit against LaPierre and top NRA leaders in August 2020, leading to Friday's verdict.

"In New York, you cannot get away with corruption and greed, no matter how powerful or influential you think you may be," James said after the verdict was announced, in a post on X, the former Twitter.

"Everyone, even the NRA and Wayne LaPierre, must play by the same rules," James added.

She called this "a major victory," which comes on top of a judge's recent order against former president Donald Trump to pay at least US$355 million in penalties for business fraud -- another case brought by James.

LaPierre and NRA senior management misappropriated millions of dollars in NRA funds to pay for a lavish lifestyle that included private jets, expensive meals, and family trips to the Bahamas, James said before the trial started.

"The NRA, as a New York-registered not-for-profit, charitable corporation, has legal obligations to use its funds for charitable purposes, not to support the lavish lifestyles of senior management and organisation insiders," she said.

"(The) investigation found that instead of serving NRA members, senior management blatantly disregarded New York state and federal laws, and even internal NRA policies."

In January, James' office announced that Joshua Powell, the NRA's former executive director of operations and chief of staff to LaPierre, had reached a US$100,000 agreement with her office. Powell was one of five defendants in the lawsuit.

The 150-year-old NRA is the leading promoter of gun rights in the United States and has focused its efforts since the 1970s on battling gun restrictions.

Polls have showed time and again that the majority of Americans want greater gun control, in a country where mass shootings occur regularly, schoolchildren are subjected to routine shooter drills, and there are more guns than people.

But politicians have repeatedly failed to reform gun laws.

From 2000 to 2012, the NRA and its allies in the firearms industry combined to pour US$80 million into US congressional and presidential races, according to an analysis by the Centre for Responsive Politics.

In the 2016 presidential election, the NRA spent about US$20 million for ads attacking Democrat Hillary Clinton and another US$10 million for ads supporting Republican Donald Trump. (AFP)